Turn on the Replay Buffer in OBS by going to File->Preferences->Output->Enable Replay Buffer. You also want to check General->Automatically start replay buffer when streaming.
Then, in Hotkeys, set a Hotkey to Save Replay. When something cool happens, press that key. This will save the last few seconds of footage to a video file.
From there you can use the Instant Replay script included with OBS (Tools->Scripts->add instant-replay.lua). Set it up to a media source, and a hotkey for Instant Replay in preferences, and it will automatically play the last saved replay in the Media Source when you press that Instant Replay hotkey.
Note that the replay buffer records the entire screen, so you might have to do some clever cropping etc. if you want to only show the playfield portion of the replay. But those are the basics.